Electron Leak? Raging Torrent!

Our columnist revisits how technology wastes power, why the problem worsens, and what to do.

Since I wrote "The Electron Leak" (October 5), which addressed the issue of standby power and how much electricity our computers consume, I think I've heard from most of the electrical engineers on PC Magazine's subscriber list. Most complained that I'd probably done the measurements wrong by using improper instruments for AC voltage and current, or I'd ignored the difference between volt-amps and watts.

I did, in fact, use a calibrated rms (root-mean-square) voltmeter appropriate for AC measurement and an accurate AC ammeter with resolution in the milliamp range. But I measured volt-amps, not watts.

One of the challenging things about measuring AC power consumption is that current consumption is not constant, since the voltage varies continually. An ammeter is likely to read the peak value, while the average current consumed is much lower. The power factorthe phase relationship between AC voltage and currentis another wrinkle. As reader Gary Handova (and numerous others) explained:

Current is not necessarily in phase with the voltage. An example would be equipment that is powered by a transformer. When no power is being consumed, the transformer will still have a significant "excitation current." This current is 90 degrees out of phase with the voltage and will not register on a power meter. There is also some loss that does consume true power, but this is typically much less than the excitation current.

Your power company sells you watts, not volt-amps, and it takes true current consumption to spin the electric meter. But the power factor can be affected by capacitive and inductive loading on the line as well as by the devices that are using the juice. And while it's generally close enough to base your billing on, it's never perfect.

I remember all of that theory from my high-school electronics classes. I also remember the bench testing we did with instruments, motors, and transformers under varying loads. We quickly discovered that transformers wandered pretty far from the theoretical ideal and that most consumed real power all the time, whether they were loaded or not.

You can verify this in a very unscientific way just by touching some wall wartsyour basic, cheap, transformer-based power supply. You'll find that some are warm, even though they're not charging anything or the equipment is off. The cheesy, lossy transformers are a problem, as are poorly designed power-filtering circuits. If there's thermal rise, there's power consumption. For much of the equipment I was measuring, the power factor isn't that far off, and VA is pretty close to watts. The damage is cumulative: 50 megawatts here, 100 MW there, and you've got gigawatts of wasted power across the country.

I also verified my findings with published numbers on various government and industrial Web sites, and again, I was pretty close. When I shared that with some of the folks who wrote to me, they told me to be suspicious of the numbers, that the government and industry had a vested interest in not building more power plants and in putting the onus of conservation on the consumer.

Whether that's true or not is hardly the point; the real issues are keeping millions of tons of pollutants out of the air, lowering the consumption of fossil fuels, decreasing our dependence on imported fuels, and freeing headroom in our electrical supply system that may amount to 5 or 10 percent of the total. And for all that, the onus is on us, and on the industry.

Microsoft and Intel influence many aspects of PC design, far beyond the operating system and the chips. Intel is currently pushing for more efficiency in the power supply in future PCs, which will mean cooler operation and less power consumption.

Chris Calwell, research director of Ecos Consulting, has done research for the EPA and worked with Intel on efficiency. He points out that laptops are, on average, five times more energy-efficient than desktops, and can be even more so. A shocking 95 percent of users don't bother to enable any power management features when the system is on AC powerwhen the savings, both in power conserved and longevity of the system, can be dramatic. Many desktops have power-conserving modes, which often go unused.

Meanwhile, desktop power supplies need an efficiency overhaul to counteract another trend: Graphics card power consumption is rising much faster than any other component in the system, potentially doubling between this year and nextmaking it by far the hungriest component in the system. Check out http://www.80plus.org for an understanding of the improvements that can be made.

Bill Machrone is vice president of technology at Ziff Davis Publishing and editorial director of the Interactive Media and Development Group. He joined Ziff Davis in May 1983 as technical editor of PC Magazine, became editor-in-chief in September of that year, and held that position for the next eight years, while adding the titles of publisher and publishing director. During his tenure, Machrone created the tough, labs-based comparison reviews that propelled PC Magazine to the forefront of the industry and made it the seventh-largest magazine...
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